Fluid-distensible, load sustaining bag rollers and vehicles incorporating such bag rollers (as disclosed in my prior U.S. patents referred to above) provide a number of important operating advantages for off-road operation.
It is a primary objective of the present invention to further improve vehicles of this kind and the bag rollers to achieve improvements in operation, particularly to permit increased speed in off-road and in on-highway use.
The bag roller of the present invention is an axially elongated bag roller which has a substantially different shape from the torroidal shape of pneumatic tires. The axially elongated bag roller of the present invention is also constructed different from the way in which a torroidal tire is constructed and functions in a way different from a tire.
The axially elongated bag roller of the present invention is constructed to provide maximum flexibility in the walls and tread area of the bag roller while eliminating carcass restraining areas to thereby minimize carcass stresses and also to provide increased bag life.
The ideal bag roller construction of the present invention has precise alignment of longitudinal and circumferential cords in the carcass and precise positioning of those cords in distinct layers in the carcass. This provides an ideal pneumatic bag roller which co-acts with the related top roller and with the terrain traversed by the vehicle to produce a mode of bag operation which is different and better than that which could be obtained by the prior art.
The ideal bag roller construction of the present invention provides a bag shape in which the circumferential cords interact nonstretchably with the top roller, similar to the interaction between a conveyor belt and its driving pulley. This construction provides a highly flexible quality of the shoulder area of the bag roller so that the pneumatic bag roller can accommodate the severe curvilinear flexure that occurs each quarter revolution of the bag roller under certain conditions of load and operation of the vehicle.
The ideal bag roller construction of the present invention permits all the cords to work in tension when the bag is inflated and under load in torque. It enables the bag roller to obtain the maximum amount of wrap around of the bag roller around the top roller. It accomplishes the desirability of a large foot print to permit distributing large loads for the minimum ground bearing pressure concentraion while also providing flexibility for the tread area itself to enable the foot print area to conform to the ground surface and to irregularities in the ground surface with minimal localized concentration of the load within the tread area. And it permits a bag roller to operate effectively in both off-road operation and on-highway use (where the flexure of the side wall at high speed operation can produce a particular problem of excessive stress or wear if the bag roller is not properly constructed).
The ideal bag roller has a tread area which is in the the form of a right circular cylinder when fully inflated without load so as to minimize the scuffing of the bag on the ground during operation.
Both Applicant's prior U.S. Pat. No. Re. 24,272 and U.S. Pat. No. 2,802,541 disclosed elliptically shaped rollers, rather than a bag roller construction that provides a cylindrical tread area. The entire teaching of Applicant's U.S. Pat. No. 2,802,541 was directed toward a geometrical relationship between a crowned bag roller and a crowned top roller. See FIG. 6 of U.S. Pat. No. 2,802,541 and FIG. 7 and the related disclosure and specification. See also Column 2, line 31-72 of U.S. Pat. No. 2,802,541.
Applicant's U.S. Pat. No. Re. 24,272 does not disclose a bag carcass having the desired orientation (to be described in more detail below) of the longitudinal radial and circumferential cords of the carcass of the bag roller of the present invention. Instead, the U.S. Pat. No. Re. 24,272 discloses (see in particular Column 4, lines 30-45 of the U.S. Pat. No. Re. 24,272) a construction of the roller in which layers of rubber impregnated nylon fabric in "orange peel" sections are used and joined by cemented laps 53 and in which the layers of rubber impregnated nylon fabric 54 are then wound over the structure formed by the fabric section 52.
In 1952, when the application for U.S. Pat. No. Re. 24,272 was filed, rubber impregnated fabric was a square woven fabric and was usually cut on a bias. The overlap of the fabric sections set up a rigid cross fabric structure which introduced stress areas subject to rupture. Furthermore, in an "orange peel" section all of the cords do not go from hub to hub like the longitudinal radial cords of the present bag roller invention (as will be described in more detail below).
Thus, neither Applicant's prior U.S. Pat. No. Re. 24,272 nor Applicant's prior U.S. Pat. No. 2,802,541 could provide the operating and durability benefits of the ideal bag construction of the present invention.
It is a specific object of the present invention to construct the bag roller in a way that: (1) provides maximum flexibility in the walls and tread area of the bag roller and to thereby maximize the ability of the bag roller to conform to the terrain with minimum distrubance of the terrain; (2) provides maximum dynamic bag balancing for increased speeds; and (3) eliminates carcass restraining areas to minimize carcass stresses and to thus provide increased bag life.